Curable composition with improved mechanical properties and high transparency

ABSTRACT

wherein R1 is same or different and is, independently from one another, selected from the group consisting of a hydrogen atom and hydrocarbon residues having 1 to 12 carbon atoms, R2 is same or different and is, independently from one another, selected from hydrocarbon residues having 1 to 12 carbon atoms, Ar is selected from aryl groups, and n is an integer selected from 3 to 9; and adhesive, sealant, or coating materials comprising the composition and use thereof.

The present invention relates to the field of curable compositions, asused for example in adhesives, sealants and coating compositions. Inparticular, the invention relates to moisture curable compositions basedon silane-terminated polymers, their use as an adhesive, sealant and/orcoating material, and adhesive, sealant and/or coating materialscomprising the moisture curable composition.

One-component, moisture-curing adhesives and sealants have for yearsplayed an important part in numerous technical applications. As well asthe polyurethane adhesives and sealants with free isocyanate groups andthe traditional silicone adhesives and sealants based ondimethylpolysiloxanes, there has recently also been increasing use ofso-called silane-terminated adhesives and sealants. Compared withpolyurethane adhesives and sealants, the silane-terminated adhesives andsealants have the advantage that they are free from isocyanate groups,in particular from monomeric diisocyanates. Furthermore, they aredistinguished by a broad range of adhesion to a wide variety ofsubstrates without any surface pretreatment using primers.

Polymer systems having reactive silyl groups are therefore known inprinciple. In the presence of atmospheric moisture, polymers havingsilyl groups with hydrolyzable substituents are already capable ofcondensing with one another at room temperature, splitting off thehydrolyzed residues. Depending on the concentration of silyl groupshaving hydrolyzable substituents and the structure of these silylgroups, mainly long-chain polymers (thermoplastics), relativelywide-mesh, three-dimensional networks (elastomers) or highly crosslinkedsystems (thermosets) are formed during this process. The polymersgenerally comprise an organic backbone which carries, for example,alkoxysilyl or acyloxysilyl groups at the ends. The organic backbone canbe, for example, polyurethanes, polyesters, polyethers, etc.

Polymers with silyl groups at the ends or in a side chain are describedfor example in EP 1 396 513 A1. The silyl groups having hydrolyzablesubstituents are introduced, according to this document, by addition ofa hydrosilane to terminal double bonds of the backbone polymer, byreaction of isocyanatosilanes with hydroxyl groups of the polymer, byreaction of silanes comprising active hydrogen atoms withisocyanate-functionalized polymers or by reaction of mercaptosilaneswith terminal double bonds of the polymer. The polymers are a componentof compositions which are used as adhesives or sealants.

EP 1 535 940 A1 also describes a method for producing crosslinkablematerials, wherein in a first step organyloxysilyl-terminated polymersare produced by reacting dihydroxy-terminated polymers withisocyanato-functional silanes and these are mixed in a second step withsilane condensation catalyst and optionally further substances.

A curable composition based on silyl groups which can crosslink bysiloxane bond formation is also provided by EP 1 930 376 A1, wherein anamine compound constituting a silanol condensation catalyst is listed asa further component.

A crosslinkable polymeric composition based on silane-terminatedpolymers having mixed oxyalkylene units in the polymer backbone isdescribed in WO 2005/047394 A1.

WO 2010/063740 A1 discloses an adhesive or sealant comprising silylatedpolyurethanes, silylated polyureas, silylated polyethers, silylatedpolysulfides and silyl-terminated acrylates, as well as acyclohexanepolycarboxylic acid derivative.

A need still exists for compositions based on the silane-terminatedpolymers for use in adhesives, sealants and coatings that exhibitimproved performance, in particular, mechanical properties after curing.In addition, the compositions should also meet all other conventionalrequirements of a modern adhesive, sealant and/or coating composition.

The object of the present invention is therefore to provide a curablecomposition having improved mechanical properties, in particular reducedskin over time, high tensile strength while maintaining acceptableelongation, and improved optical properties, in particular hightransparency.

It has been found surprisingly that this object is achieved by the useof a specific combination of certain silicone compound(s) in acomposition based on silane-terminated polymers. The invention thereforeprovides a curable composition, which at least comprises

a) at least one polymer having at least one terminal group of thegeneral formula (I)-A_(n)-R—SiXYZ  (I),

-   -   wherein    -   A is a divalent or trivalent bonding group containing at least        one heteroatom,    -   R is selected from divalent hydrocarbon residues having 1 to 12        carbon atoms,    -   X, Y, Z are, independently of one another, selected from the        group consisting of a hydroxyl group and C₁ to C₈ alkyl, C₁ to        C₈ alkoxy, C₁ to C₈ acyloxy groups and —CH₂—N—R′ wherein N is        oxygen, nitrogen or sulfur, preferably oxygen, and R′ is        selected from C₁ to C₈ alkyl groups, preferably a methyl group,

wherein X, Y, Z are substituents directly bound with the Si atom or thetwo of the substituents X, Y, Z form a ring together with the Si atom towhich they are bound and at least one of the substituents X, Y, Z isselected from the group consisting of a hydroxyl group, C₁ to C₈ alkoxyand C₁ to C₈ acyloxy groups, and

-   -   n is 0 or 1; and

b) at least one compound of the general formula (II)

-   -   wherein R¹ is same or different and is, independently from one        another, selected from the group consisting of a hydrogen atom        and hydrocarbon residues having 1 to 12 carbon atoms, preferably        selected from hydrocarbon residues having 1 to 6 carbon atoms,        more preferably methyl or ethyl group,    -   R² is same or different and is, independently from one another,        selected from hydrocarbon residues having 1 to 12 carbon atoms,        preferably selected from hydrocarbon residues having 1 to 6        carbon atoms, more preferably a methyl or ethyl group,    -   Ar is selected from aryl groups, preferably a phenyl group, and    -   n is an integer selected from 3 to 9, preferably 3 to 6, more        preferably 3 or 4.

A “composition” is understood in the context of the present invention asa mixture of at least two ingredients.

The term “curable” is to be understood to mean that, under the influenceof external conditions, in particular under the influence of moisturepresent in the environment and/or supplied for the purpose, thecomposition can pass from a relatively flexible state, optionallypossessing plastic ductility, to a harder state. In general, thecrosslinking can take place by means of chemical and/or physicalinfluences, i.e. as well as the already mentioned moisture, for example,by the supply of energy in the form of heat, light or otherelectromagnetic radiation, but also by simply bringing the compositioninto contact with air or a reactive component.

In preferred embodiments, the polymer a) has at least two terminalgroups of the general formula (I).

The polymer having the at least one terminal group of the generalformula (I) is preferably a polyether, a poly(meth)acrylic acid ester,or a polyurethane.

A “polyether” is understood to be a polymer in which the organicrepeating units comprise ether functionalities C—O—C in the main chain.Polymers having lateral ether groups, such as cellulose ethers, starchethers and vinyl ether polymers, as well as polyacetals such aspolyoxymethylene (POM) are not included in the polyethers.

A “poly(meth)acrylic acid ester” is understood to be a polymer based on(meth)acrylic acid esters, which therefore has as a repeating unit thestructural motif —CH₂—CR^(a)(COOR^(b))—, where R^(a) denotes a hydrogenatom (acrylic acid ester) or a methyl group (methacrylic acid ester) andRb denotes linear alkyl residues, branched alkyl residues, cyclic alkylresidues and/or alkyl residues comprising functional substituents, forexample methyl, ethyl, isopropyl, cyclohexyl, 2-ethylhexyl or2-hydroxyethyl residues.

A “polyurethane” is understood to be a polymer which has at least twourethane groups —NH—CO—O— in the main chain.

The polymer having at least one terminal group of the general formula(I) is particularly preferably a polyether. Polyethers have a flexibleand elastic structure, with which compositions having excellent elasticproperties can be produced. Polyethers are not only flexible in theirbackbone, but at the same time strong. Thus, for example, polyethers arenot attacked or decomposed by water and bacteria, in contrast to, e.g.,polyesters, for example.

The number average molecular weight M_(n) of the polyether on which thepolymer is based is for preference 2000 to 100,000 g/mol (daltons),particularly preferably at least 6000 g/mol and in particular at least8000 g/mol. Number average molecular weights of at least 2000 g/mol areadvantageous for the polyethers of the present invention, becausecompositions according to the invention based on polyethers with such aminimum molecular weight have significant film-forming properties. Forexample, the number average molecular weight M_(n) of the polyether is4000 to 100,000, preferably 8000 to 50,000, particularly preferably10,000 to 30,000 and in particular 10,000 to 25,000 g/mol. Thesemolecular weights are particularly advantageous, since the correspondingcompositions have a balanced ratio of viscosity (ease of processing),strength and elasticity.

Particularly advantageous viscoelastic properties can be achieved ifpolyethers having a narrow molecular weight distribution, and thus lowpolydispersity, are used. These can be produced, for example, byso-called double metal cyanide catalysis (DMC catalysis). Polyethersproduced in this way are distinguished by a particularly narrowmolecular weight distribution, by a high average molecular weight and bya very low number of double bonds at the ends of the polymer chains.

In a special embodiment of the present invention, the maximumpolydispersity M_(w)/M_(n) of the polyether on which the polymer isbased is therefore 3, particularly preferably 1.7 and most particularlypreferably 1.5.

The number average molecular weight M_(n), as well as the weight averagemolecular weight M_(w), is determined according to the present inventionby gel permeation chromatography (GPC, also known as SEC) at 23° C.using a styrene standard. This method is known to one skilled in theart. The polydispersity is derived from the average molecular weightsM_(w) and M_(n). It is calculated as PD=M_(w)/M_(n).

The ratio M_(w)/M_(n) (polydispersity) indicates the width of themolecular weight distribution and thus of the different degrees ofpolymerization of the individual chains in polydisperse polymers. Formany polymers and polycondensates, a polydispersity value of about 2applies. Strict monodispersity would exist at a value of 1. A lowpolydispersity of, for example, less than 1.5 indicates a comparativelynarrow molecular weight distribution, and thus the specific expressionof properties associated with molecular weight, such as e.g., viscosity.In particular, therefore, in the context of the present invention, thepolyether on which the polymer A is based has a polydispersity(M_(w)/M_(n)) of less than 1.3.

In preferred embodiments of the present invention, the polymer having atleast one terminal group of the general formula (I) can be apolyurethane obtainable by reacting at least i) a polyol or a mixture oftwo or more polyols and ii) a polyisocyanate or a mixture of two or morepolyisocyanates.

A “polyol” is understood to be a compound which contains at least two OHgroups, irrespective or whether the compound contains other functionalgroups. However, a polyol used in accordance with the present inventionpreferably contains only OH groups as functional groups or, if otherfunctional groups are present, none of these other functional groups isreactive at least to isocyanates under the conditions prevailing duringthe reaction of the polyol(s) and polyisocyante(s).

The polyols suitable for preparing the polyurethane according to theinvention are preferably polyether polyol. The above descriptions aboutthe molecular weight and polydispersity of the polyether apply to thepolyether polyol. The polyether polyol is preferably a polyalkyleneoxide, particularly preferably polyethylene oxide and/or polypropyleneoxide. In preferred embodiments, a polyether or a mixture of twopolyethers are used.

The polyols to be used in accordance with the invention have an OH valueof preferably about 5 to about 15 and, more preferably, of about 10. Thepercentage content of primary OH groups should be below about 20%, basedon all the OH groups, and is preferably below 15%. In one particularlyadvantageous embodiment, the acid value of the polyethers used is belowabout 0.1, preferably below 0.05 and, more preferably, below 0.02.

Besides the polyethers, the polyol mixture may contain other polyols.For example, it may contain polyester polyols with a molecular weight ofabout 200 to about 30,000.

A “polyisocyanate” is understood to be a compound which has at least twoisocyanate groups —NCO. This compound does not have to be a polymer, andinstead is frequently a low molecular compound.

The polyisocyanates suitable for preparing the polyurethane according tothe invention include ethylene diisocyanate, 1,4-tetramethylenediisocyanate, 1,4-tetramethoxybutane diisocyanate, 1,6-hexamethylenediisocyanate (HDI), cyclobutane-1,3-diisocyanate,cyclohexane-1,3-and-1,4-diisocyanate, bis(2-isocyanatoethyl)fumarate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate, IPDI), 2,4- and 2,6-hexahydrotoluylene diisocyanate,hexahydro-1,3-or-1,4-phenylene diisocyanate, benzidine diisocyanate,naphthalene-1,5-diisocyanate, 1,6-diisocyanato-2,2,4-trimethylhexane,1,6-diisocyanato-2,4,4-trimethylhexane, xylylene diisocyanate (XDI),tetramethylxylylene diisocyanate (TMXDI), 1,3- and 1,4-phenylenediisocyanate, 2,4-or 2,6-toluylene diisocyanate (TDI),2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, or4,4′-diphenylmethane diisocyanate (MDI), and the isomeric mixturesthereof. Also suitable are partially or completely hydrogenatedcycloalkyl derivatives of MDI, for example completely hydrogenated MDI(H12-MDI), alkyl-substituted diphenylmethane diisocyanates, for examplemono-, di-, tri-, or tetraalkyldiphenylmethane diisocyanate and thepartially or completely hydrogenated cycloalkyl derivatives thereof,4,4′-diisocyanatophenylperfluorethane, phthalic acid-bis-isocyanatoethylester, 1 chloromethylphenyl-2,4-or-2,6-diisocyanate,1-bromomethylphenyl-2,4-or-2,6-diisocyanate, 3,3′-bis-chloromethylether-4,4′-diphenyl diisocyanate, sulfur-containing diisocyanates suchas those obtainable by reacting 2 moles diisocyanate with 1 molethiodiglycol or dihydroxydihexyl sulfide, diisocyanates of dimer fattyacids, or mixtures of two or more of the named diisocyanates. Thepolyisocyanate is preferably IPDI, TDI or MDI.

Other polyisocyanates suitable for use in accordance with the inventionare isocyanates with a functionality of three or more obtainable, forexample, by oligomerization of diisocyanates, more particularly byoligomerization of the isocyanates mentioned above. Examples of suchtri- and higher isocyanates are the triisocyanurates of HDI or IPDI ormixtures thereof or mixed triisocyanurates thereof and polyphenylmethylene polyisocyanate obtainable by phosgenation ofaniline/formaldehyde condensates.

According to the invention, there is preferably a stoichiometric excessof NCO groups of the polyisocyanates with respect to the hydroxy groupsof the polyols, “the polyols” and “the polyisocyanates” in each casealso encompassing the presence of only one polyol and/or only onepolyisocyanate. This stoichiometric excess must exist under the processconditions; i.e., it is not sufficient when the excess is nominallypresent, but a portion of the NCO groups of the polyisocyanates reactswith reactants other than the OH groups of the polyols, for example withmonofunctional alcohols, so that there is a de facto shortage of NCOgroups of the polyisocyanates with respect to the OH groups of thepolyols. The ratio of the number of OH groups of the polyols to thenumber of NCO groups of the polyisocyanates is particularly preferably1:3 to 1:1.1, in particular 1:2.5 to 1:1.5.

The at least one polymer of the curable composition according to theinvention has at least one terminal group of the general formula (I)-A_(n)-R—SiXYZ  (I),wherein A is a divalent or trivalent bonding group containing at leastone heteroatom, R is selected from divalent hydrocarbon residues having1 to 12 carbon atoms, X, Y, Z are, independently of one another,selected from the group consisting of a hydroxyl group and C₁ to C₈alkyl, C₁ to C₈ alkoxy, C₁ to C₈ acyloxy groups and —CH₂—N—R′ wherein Nis oxygen, nitrogen or sulfur, preferably oxygen, and R′ is selectedfrom C₁ to C₈ alkyl groups, preferably a methyl group, wherein X, Y, Zare substituents directly bound with the Si atom or the two of thesubstituents X, Y, Z form a ring together with the Si atom to which theyare bound, and at least one of the substituents X, Y, Z is selected fromthe group consisting a hydroxyl group, C₁ to C₈ alkoxy and C₁ to C₈acyloxy groups, and n is 0 or 1.

In this context, the divalent or trivalent bonding group A comprising atleast one heteroatom is understood to be a divalent or trivalentchemical group which links the polymer backbone of the silane-terminatedpolymer with the residue R of the formula (I). For example, the divalentor trivalent linking group A can be formed for example during theproduction of the alkoxysilane- and/or acyloxysilane-terminated polymer,for example as an amide or urethane group by the reaction of a polyetherwhich is functionalized with hydroxy groups with an isocyanatosilane.The linking group can be either capable or incapable of beingdifferentiated from structural features occurring in the underlyingpolymer backbone. The latter is the case, for example, if it isidentical with the linking points of the repeating units of the polymerbackbone.

The index “n” corresponds to 0 (zero) or 1, i.e. the divalent ortrivalent linking group A links the polymer backbone with the residue R(n=1) or the polymer backbone is bound or linked directly with theresidue R (n=0).

The divalent or trivalent linking group A in the general formula (I) ispreferably an oxygen atom or an

group, where R″ is selected from the group consisting of a hydrogen atomand alkyl or aryl residues having 1 to 12 carbon atoms, or is asubstituted or unsubstituted amide, carbamate, urethane, urea, imino,carboxylate, carbamoyl, amidino, carbonate, sulfonate or sulfinategroup. Particularly preferred as linking group A are urethane and ureagroups, which can be obtained by reacting certain functional groups of aprepolymer with an organosilane which carries a further functionalgroup. Urethane groups can be formed, for example, either when thepolymer backbone comprises terminal hydroxy groups and isocyanatosilanesare used as a further component, or conversely when a polymer havingterminal isocyanate groups is reacted with an alkoxysilane comprisingterminal hydroxy groups. Similarly, urea groups can be obtained if aterminal primary or secondary amino group—either on the silane or on thepolymer—is used, which reacts with a terminal isocyanate group that ispresent in the respective reactant. This means that either anaminosilane is reacted with a polymer having terminal isocyanate groupsor a polymer that is terminally substituted with an amino group isreacted with an isocyanatosilane.

Urethane and urea groups advantageously increase the strength of thepolymer chains and of the overall crosslinked polymer.

The residue R is a divalent hydrocarbon residue having 1 to 12 carbonatoms. The hydrocarbon residue can be a linear, branched or cyclicalkylene residue. The hydrocarbon residue can be saturated orunsaturated. R is preferably a divalent hydrocarbon residue having 1 to6 carbon atoms. The curing rate of the composition can be influenced bythe length of the hydrocarbon residues which form one of the bindinglinks or the binding link between polymer backbone and silyl residue.Particularly preferably, R is a methylene, ethylene or n-propylenegroup, in particular a methylene or n-propylene residue.

Alkoxysilane-terminated compounds having a methylene group as bindinglink to the polymer backbone—so-called “alpha-silanes”—have aparticularly high reactivity of the terminating silyl group, leading toreduced setting times and thus to very rapid curing of formulationsbased on these polymers.

In general, a lengthening of the binding hydrocarbon chain leads toreduced reactivity of the polymers. In particular, “gamma-silanes”—whichcomprise the unbranched propylene residue as binding link—have abalanced ratio between necessary reactivity (acceptable curing times)and delayed curing (open assembly time, possibility of corrections afterbonding). By carefully combining alpha- andgamma-alkoxysilane-terminated building blocks, therefore, the curingrate of the systems can be influenced as desired.

Within the context of the present invention, R is most particularlypreferably an n-propylene group.

The substituents X, Y and Z in the general formula (I) are,independently of one another, selected from the group consisting of ahydroxyl group and C₁ to C₈ alkyl, C₁ to Ca alkoxy, C₁ to C₈ acyloxygroups and —CH₂—N—R′ wherein N is oxygen, nitrogen or sulfur, preferablyoxygen, and R′ is selected from C₁ to C₈ alkyl groups, preferably amethyl group, wherein at least one of the substituents X, Y, Z here mustbe a hydrolyzable group, preferably a C₁ to C₈ alkoxy or a C₁ to C₈acyloxy group, wherein the substituents X, Y and Z are directly boundwith the Si atom or the two of the substituents X, Y, Z form a ringtogether with the Si atom to which they are bound. In preferredembodiments, X, Y and Z are the substituents directly bound with the SIatom. As hydrolyzable groups, preferably alkoxy groups, in particularmethoxy, ethoxy, i-propyloxy and i-butyloxy groups, are selected. Thisis advantageous, since no substances which irritate mucous membranes arereleased during the curing of compositions comprising alkoxy groups. Thealcohols formed by hydrolysis of the residues are harmless in thequantities released, and evaporate. These compositions are thereforesuitable in particular for the DIY sector. However, acyloxy groups, suchas an acetoxy group —O—CO—CH₃, can also be used as hydrolyzable groups.

In preferred embodiments, the alkoxy- and/or acyloxysilane-terminatedpolymer(s) has/have at least two terminal groups of the general formula(I). Each polymer chain thus comprises at least two linking points atwhich the condensation of the polymers can be completed, splitting offthe hydrolyzed residues in the presence of atmospheric moisture. In thisway, regular and rapid crosslinkability is achieved so that bonds withgood strengths can be obtained. In addition, by means of the quantityand the structure of the hydrolyzable groups—for example by using di- ortrialkoxysilyl groups, methoxy groups or longer residues—theconfiguration of the network that can be achieved as a long-chain system(thermoplastics), relatively wide-mesh three-dimensional network(elastomers) or highly crosslinked system (thermosets) can becontrolled, so that inter alia the elasticity, flexibility and heatresistance of the finished crosslinked compositions can be influenced inthis way.

In preferred embodiments, in the general formula (I), X is preferably analkyl group and Y and Z are, each independently of one another, analkoxy group, or X, Y and Z are, each independently of one another, analkoxy group. In general, polymers comprising di- or trialkoxysilylgroups have highly reactive linking points which permit rapid curing,high degrees of crosslinking and thus good final strengths. Theparticular advantage of dialkoxysilyl groups lies in the fact that,after curing, the corresponding compositions are more elastic, softerand more flexible than systems comprising trialkoxysilyl groups. Theyare therefore suitable in particular for use as sealants. In addition,they split off even less alcohol during curing and are therefore ofparticular interest when the quantity of alcohol released is to bereduced.

With trialkoxysilyl groups, on the other hand, a higher degree ofcrosslinking can be achieved, which is particularly advantageous if aharder, stronger material is desired after curing. In addition,trialkoxysilyl groups are more reactive and therefore crosslink morerapidly, thus reducing the quantity of catalyst required, and they haveadvantages in “cold flow”—the dimensional stability of a correspondingadhesive under the influence of force and possibly temperature.

Particularly preferably, the substituents X, Y and Z in the generalformula (I) are, each independently of one another, selected from ahydroxyl, a methyl, an ethyl, a methoxy or an ethoxy group, oralkoxymethyl group, preferably methoxymethyl group, at least one of thesubstituents being a hydroxyl group, or a methoxy or an ethoxy group,preferably a methoxy group. Methoxy and ethoxy groups as comparativelysmall hydrolyzable groups with low steric bulk are very reactive andthus permit a rapid cure, even with low use of catalyst. They aretherefore of particular interest for systems in which rapid curing isdesirable, such as for example in adhesives with which high initialadhesion is required.

Interesting configuration possibilities are also opened up bycombinations of the two groups. If, for example, methoxy is selected forX and ethoxy for Y within the same alkoxysilyl group, the desiredreactivity of the terminating silyl groups can be adjusted particularlyfinely if silyl groups carrying exclusively methoxy groups are deemedtoo reactive and silyl groups carrying ethoxy groups not reactive enoughfor the intended use.

In addition to methoxy and ethoxy groups, it is of course also possibleto use larger residues as hydrolyzable groups, which by nature exhibitlower reactivity. This is of particular interest if delayed curing isalso to be achieved by means of the configuration of the alkoxy groups.

The total proportion of the polymers with at least onesilicone-containing group, preferably at least one end group, of thegeneral formula (I) in the composition according to the invention ispreferably 10 to 80 wt. %, more preferably 10 to 60 wt. %, mostpreferably 20 to 60 wt. %, based in each case on the total weight of thecurable composition.

The curable composition according to the invention comprises as anadditional component at least one compound of the general formula (II)

wherein R¹ is same or different and is, independently from one another,selected from the group consisting of a hydrogen atom and hydrocarbonresidues having 1 to 12 carbon atoms, preferably selected fromhydrocarbon residues having 1 to 6 carbon atoms, more preferably methylor ethyl group, R² is same or different and is, independently from oneanother, selected from hydrocarbon residues having 1 to 12 carbon atoms,preferably selected from hydrocarbon residues having 1 to 6 carbonatoms, more preferably a methyl or ethyl group, Ar is selected from arylgroups, preferably a phenyl group, and n is an integer selected from 3to 9, preferably from 3 to 6, more preferably from 3 or 4. In preferredembodiments, the aryl group is a phenyl group and/or R¹ is selected froma methyl or ethyl group, more preferably a methyl group and/or R² isselected from is selected from a methyl or ethyl group, more preferablya methyl group.

The most preferred is phenyldimethoxysilane-endcapped PDMS as follows:

wherein n is selected from 3 to 9, preferably from 3 to 6, morepreferably from 3 or 4.

It has been shown that, when using the at least one compound of thegeneral formula (II) above in combination with the polymer having atleast one terminal group of the general formula (I), the curablecompositions according to the invention have improved mechanicalproperties, in particular reduced skin over time, high tensile strengthwhile maintaining acceptable elongation, and improved opticalproperties, in particular high transparency.

The proportion of compound of the general formula (II) in the curablecomposition according to the invention is preferably 1 to 60 wt. %, morepreferably 2 to 50 wt. % based on the total weight of the composition.

The composition according to the invention may comprise furtheringredients in addition to the components mentioned hitherto, which cancontribute to the expression of desired properties. Thus, it may benecessary to add one or more plasticizers to adjust the elasticproperties and to improve the processability of the composition. Aplasticizer is understood to be a substance which reduces the viscosityof the composition and thus makes processing easier, and in additionimproves flexibility and extensibility of the compositions.

The plasticizer is preferably selected from a fatty acid ester, adicarboxylic acid ester (except cyclohexanedicarboxylic acid dialkylester), an ester of epoxidized fatty acids or fatty acids carrying OHgroups, a fat, a glycolic acid ester, a benzoic acid ester, a phosphoricacid ester, a sulfonic acid ester, a trimellitic acid ester, anepoxidized plasticizer, a polyether plasticizer, a polystyrene, ahydrocarbon plasticizer and a chlorinated paraffin, and mixtures of twoor more thereof. By the careful selection of one of these plasticizersor of a specific combination, further advantageous properties of thecomposition according to the invention, for example gelling propertiesof the polymers, low-temperature elasticity or low-temperatureresistance or antistatic properties, can be achieved.

Among the polyether plasticizers, preferably end-capped polyethyleneglycols are used, for example polyethylene or polypropylene glycoldi-C₁₋₄-alkyl ethers, in particular the dimethyl or diethyl ethers ofdiethylene glycol or dipropylene glycol, and mixtures of two or morethereof. Also suitable as plasticizers are, for example, esters ofabietic acid, butyric acid ester, acetic acid ester, propionic acidester, thiobutyric acid ester, citric acid ester and esters based onnitrocellulose and polyvinyl acetate, as well as mixtures of two or morethereof. Also suitable are, for example, the asymmetrical esters ofadipic acid monooctyl ester with 2-ethylhexanol (Edenol DOA, CognisDeutschland GmbH, DQsseldorf). In addition, the pure or mixed ethers ofmonofunctional, linear or branched C₄₋₁₆ alcohols or mixtures of two ormore different ethers of such alcohols are suitable as plasticizers, forexample dioctyl ether (available as Cetiol OE, Cognis Deutschland GmbH,DQsseldorf). Likewise suitable as plasticizers within the framework ofthe present invention are diurethanes, which can be produced e.g. byreaction of diols having OH end groups with monofunctional isocyanates,by selecting the stoichiometry so that substantially all free OH groupsreact fully. Any excess isocyanate can then be removed from the reactionmixture, e.g. by distillation. Another method for producing diurethanesconsists in the reaction of monofunctional alcohols with diisocyanates,wherein as far as possible all NCO groups react fully.

In principle, phthalic acid esters can also be used as plasticizers, butbecause of their toxicological potential these are not preferred.

The total quantity of plasticizer(s) in curable compositions accordingto the invention is for preference 1 to 30 wt. %, preferably 5 to 25 wt.% and particularly preferably 10 to 20 wt. %, based in each case on thetotal weight of the curable composition.

Too high a viscosity of the composition according to the invention forcertain applications can also be reduced in a simple and useful mannerby using a reactive diluent, without signs of separation (e.g.plasticizer migration) appearing in the cured material. The reactivediluent preferably has at least one functional group which reacts withe.g. moisture or atmospheric oxygen after application. Examples of thesegroups are silyl groups, isocyanate groups, vinylically unsaturatedgroups and polyunsaturated systems. As reactive diluent, it is possibleto use any compounds which are miscible with the composition accordingto the invention with a reduction of the viscosity and have at least onegroup that is reactive with the binder, individually or as a combinationof several compounds. The viscosity of the reactive diluent ispreferably less than 20,000 mPas, particularly preferably about 0.1-6000mPas, most particularly preferably 1-1000 mPas (Brookfield RVT, 23° C.,spindle 7, 10 rpm).

As reactive diluents it is possible to use for example the followingsubstances: polyalkylene glycols reacted with isocyanatosilanes (forexample Synalox 100-50B, DOW), alkyltrimethoxysilane,alkyltriethoxysilane, such as methyltrimethoxysilane,methyltriethoxysilane and vinyltrimethoxysilane (XL 10, Wacker),phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane,tetraethoxysilane, vinyldimethoxymethylsilane (XL12, Wacker),vinyltriethoxysilane (GF56, Wacker), vinyltriacetoxysilane (GF62,Wacker), isooctyltrimethoxysilane (10 Trimethoxy),isooctyltriethoxysilane (10 Triethoxy, Wacker),N-trimethoxysilylmethyl-O-methylcarbamate (XL63, Wacker),N-dimethoxy(methyl)silylmethyl-O-methylcarbamate (XL65, Wacker),hexadecyltrimethoxysilane, 3-octanoylthio-1-propyltriethoxysilane andpartial hydrolyzates of these compounds. Furthermore, the followingpolymers from Kaneka Corp. can also be used as reactive diluents: MSS203H, MS S303H, MS SAT 010 and MS SAX 350. Also suitable as reactivediluents are polymers which can be produced from an organic backbone bygrafting with a vinylsilane or by reaction of polyol, polyisocyanate andalkoxysilane.

Suitable as polyols for producing a reactive diluent are e.g., aliphaticalcohols include, for example, ethylene glycol, propylene glycol andhigher glycols, as well as other polyfunctional alcohols. The polyolscan additionally comprise other functional groups, such as e.g. esters,carbonates, amides. To produce a reactive diluent by reaction of polyolwith polyisocyanate and alkoxysilane, the corresponding polyol componentis reacted in each case with an at least difunctional isocyanate.Suitable as the at least difunctional isocyanate is in principle anyisocyanate having at least two isocyanate groups, but within theframework of the present invention, compounds having two to fourisocyanate groups, in particular two isocyanate groups, are generallypreferred. Among the alkoxysilyl groups, the di- and trialkoxysilylgroups are preferred.

The polyisocyanates described above for producing polyurethanes are alsosuitable as polyisocyanates for producing a reactive diluent.

To reduce the viscosity of the composition according to the invention,solvents can also be used as well as or instead of a reactive diluent.Suitable as solvents are aliphatic or aromatic hydrocarbons, halogenatedhydrocarbons, alcohols, ketones, ethers, esters, ester alcohols, ketoalcohols, keto ethers, keto esters and ether esters. Preferably,however, alcohols are used since in this case the storage stabilityincreases.

C₁-C₁₀ alcohols are particularly preferred, particularly methanol,ethanol, i-propanol, isoamyl alcohol and hexanol.

The composition according to the invention can additionally comprise anadhesion promoter. A_(n) adhesion promoter is understood to be asubstance which improves the adhesion properties of adhesive layers onsurfaces. It is possible to use conventional adhesion promoters known tothe person skilled in the art (tackifiers) individually or as acombination of several compounds. Suitable examples are resins, terpeneoligomers, coumarone/indene resins, aliphatic, petrochemical resins andmodified phenolic resins. Suitable within the framework of the presentinvention are, for example, hydrocarbon resins, as obtained bypolymerization of terpenes, principally α- or β-pinene, dipentene orlimonene. The polymerization of these monomers generally takes placecationically with initiation by Friedel-Crafts catalysts. The terpeneresins also include copolymers of terpenes and other monomers, e.g.styrene, α-methylstyrene, isoprene and the like. The above resins areused e.g. as adhesion promoters for pressure-sensitive adhesives andcoating materials. Also suitable are the terpene-phenolic resins whichare produced by acid-catalyzed addition of phenols to terpenes or rosin.Terpene-phenolic resins are soluble in most organic solvents and oilsand are miscible with other resins, waxes and rubber. Likewise withinthe framework of the present invention, the rosins and derivativesthereof, for example their esters or alcohols, are suitable as adhesionpromoters in the above sense. Silane adhesion promoters, in particularaminosilanes, are particularly suitable.

In a special embodiment of the curable composition according to theinvention, the composition encompasses a silane of the general formula(III)R^(1′)R^(2′)N—R^(3′)—SiXYZ  (III)as adhesion promoter, wherein R^(1′) and R^(2′) are, independently ofone another, a hydrogen or C₁ to C₈ alkyl residues, R^(3′) is a divalenthydrocarbon residue having 1 to 12 carbon atoms, optionally comprising aheteroatom, and X, Y, Z are, each independently of one another, selectedfrom a hydroxyl group or C₁ to C₈ alkyl, C₁ to C₈ alkoxy or C₁ to C₈acyloxy groups, at least one of the substituents X, Y, Z being a C₁ toC₈ alkoxy or C₁ to C₈ acyloxy group. Compounds of this type naturallyexhibit a high affinity to the binding polymer components of the curablecomposition according to the invention, but also to a wide range ofpolar and nonpolar surfaces, and therefore contribute to the formationof a particularly stable bond between the adhesive composition and theparticular substrates to be bonded.

The linking group R^(3′) can, for example, be a linear, branched orcyclic, substituted or unsubstituted alkylene residue. Nitrogen (N) oroxygen (O) may be contained therein as a heteroatom. If X, Y and/or Zare an acyloxy group, this can be e.g., the acetoxy group —OCO—CH₃.

One or more adhesion promoter(s) is/are preferably contained in thecurable composition according to the invention in a quantity of 0.1 to 5wt. %, more preferably 0.2 to 2 wt. %, in particular 0.3 to 1 wt. %,based in each case on the total weight of the composition.

The composition according to the invention may additionally comprise atleast one filler, e.g., selected from chalk, powdered limestone,precipitated and/or pyrogenic silica, zeolites, bentonites, magnesiumcarbonate, kieselguhr, alumina, clay, tallow, titanium oxide, ironoxide, zinc oxide, sand, quartz, flint, mica, powdered glass and otherground minerals. In preferred embodiments, the filler(s) areprecipitated and/or pyrogenic silica. Furthermore, organic fillers canalso be used, in particular carbon black, graphite, wood fibers, woodflour, sawdust, cellulose, cotton, pulp, wood chips, chopped straw,chaff, ground walnut shells and other short-cut fibers. Furthermore,short fibers such as glass fibers, glass filament, polyacrylonitrile,carbon fibers, Kevlar fibers or polyethylene fibers can also be added.Aluminum powder is also suitable as a filler. In addition, hollowspheres with a mineral shell or a plastic shell are suitable as fillers.These can be e.g. hollow glass spheres which are commercially availablewith the trade names Glass Bubbles®. Plastic-based hollow spheres arecommercially available, e.g. with the names Expancel® or Dualite®. Theseare composed of inorganic or organic substances, each with a diameter of1 mm or less, preferably of 500 μm or less. For some applications,fillers which make the preparations thixotropic are preferred. Thesefillers are also described as rheological auxiliaries, for examplehydrogenated castor oil, fatty acid amides or swellable plastics such asPVC. So that they can easily be squeezed out of a suitable meteringdevice (e.g. tube), these preparations possess a viscosity of 3000 to15,000, preferably 4000 to 8,000 mPas or 5000 to 6000 mPas.

The filler(s) are preferably used in a quantity of 10 to 70 wt. %, morepreferably 20 to 60 wt. %, for example 25 to 55 wt. %, in particular 35to 50 wt. %, based on the total weight of the composition according tothe invention. A_(n) individual filler or a combination of severalfillers can be used.

For example, a highly disperse silica with a BET surface area of 10 to500 m²/g is used as a filler. The use of such a silica does not bringabout a substantial increase in the viscosity of the compositionaccording to the invention but contributes to reinforcing the hardenedpreparation. By means of this reinforcement, for example the initialstrengths, tensile shear strengths and the adhesion of the adhesives,sealants or coating compositions in which the composition according tothe invention is used are improved. Preferably, uncoated silicas with aBET surface area of less than 100, more preferably less than 65 m²/g,and/or coated silicas with a BET surface area of 100 to 400, morepreferably 100 to 300, in particular 150 to 300 and most particularlypreferably 200 to 300 m²/g, are used.

As zeolites, preferably alkali aluminosilicates are used, for examplesodium-potassium aluminosilicates of the general empirical formulaaK₂O*bNa₂O*Al₂O₃*2SiO*nH₂O with 0<a, b<1 and a+b=1. The pore opening ofthe zeolite or zeolites used is just large enough to accept watermolecules. Accordingly, an effective pore opening of the zeolites ofless than 0.4 nm is preferred. Particularly preferably, the effectivepore opening is 0.3 nm+0.02 nm. The zeolite(s) is/are preferably used inthe form of a powder.

Chalk is preferably used as a filler. Cubic, non-cubic, amorphous andother modifications of calcium carbonate can be used as chalk.Preferably, the chalks used are surface treated or coated. As a coatingagent, preferably fatty acids, fatty acid soaps and fatty acid estersare used, for example lauric acid, palmitic acid or stearic acid, sodiumor potassium salts of such acids or their alkyl esters. In addition,however, other surface-active substances, such as sulfate esters oflong-chain alcohols or alkylbenzenesulfonic acids or their sodium orpotassium salts or coupling reagents based on silanes or titanates, arealso suitable. The surface treatment of chalks is often associated withan improvement in processability and adhesive strength and also theweathering resistance of the compositions. The coating composition isusually used in a proportion of 0.1 to 20 wt %, preferably 1 to 5 wt %,based on the total weight of the crude chalk.

Depending on the desired property profile, precipitated or ground chalksor mixtures thereof can be used. Ground chalks can be produced, forexample, from natural lime, limestone or marble by mechanical grinding,using either dry or wet methods. Depending on the grinding method,fractions having different average particle sizes can be obtained.Advantageous specific surface area values (BET) are between 1.5 m²/g and50 m²/g.

The composition according to the invention can additionally comprise UVstabilizers. Preferably, the proportion of the UV stabilizers in thecomposition according to the invention is up to about 2 wt. %, inparticular up to 1 wt. %. Particularly suitable as UV stabilizers arethe so-called hindered amine light stabilizers (HALS). For example, a UVstabilizer can be used which carries a silyl group and is incorporatedinto the end product during crosslinking or curing. Furthermore,benzotriazoles, benzophenones, benzoates, cyanoacrylates, acrylates,sterically hindered phenols, phosphorus and/or sulfur can also be added.The curable composition according to the invention preferably comprisesat least one bis(piperidyl) dicarboxylic acid diester, for examplebis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.

It is often useful to stabilize the composition according to theinvention further against moisture penetration in order to increase theshelf life even more. Such an improvement in shelf life can be achieved,for example, by the use of drying agents. Suitable as drying agent areall compounds that react with water to form a group that is inerttowards the reactive groups present in the composition while undergoingthe smallest possible changes in their molecular weight. Furthermore,the reactivity of the drying agents towards moisture that has penetratedinto the composition must be higher than the reactivity of the endgroups of the silyl group-containing polymer according to the inventionpresent in the composition. Isocyanates, for example, are suitable asdrying agent.

Advantageously, silanes are also used as drying agent, e.g. vinylsilanessuch as 3-vinylpropyltriethoxysilane, oxime silanes such asmethyl-O,O′,O″-butan-2-one trioximosilane or O,O′,O″,O″′-butan-2-onetetraoximosilane (CAS no. 022984-54-9 and 034206-40-1) orbenzamidosilanes such as bis(N-methylbenzamido)methylethoxysilane (CASno. 16230-35-6) or carbamatosilanes such ascarbamatomethyltrimethoxysilane. However, the use of methyl-, ethyl- orvinyltrimethoxysilane, tetramethyl- or tetraethylethoxysilane is alsopossible. Particularly preferred here are vinyltrimethoxysilane andtetraethoxysilane in terms of efficiency and costs. Also suitable asdrying agent are the above-mentioned reactive diluents, provided thatthey have a molecular weight (M_(n)) of less than about 5,000 g/mol andterminal groups whose reactivity with penetrating moisture is at leastas great as, preferably greater than, the reactivity of the reactivegroups of the silyl group-containing polymer according to the invention.Finally, alkyl orthoformates or orthoacetates can also be used as dryingagent, for example methyl or ethyl orthoformate or methyl or ethylorthoacetate. Generally, the composition according to the inventionpreferably comprises 0.01 to 10 wt. % drying agent, based on the totalweight of the composition.

The curable composition according to the invention preferably comprisesthe following components in the stated proportions by weight:

at least one polymer having at least one terminal group 10 to 60 wt. %,of the general formula (I) at least one compound of the general formula(II) 1 to 60 wt. %, at least one filler 10 to 70 wt. %, at least oneplasticizer 1 to 30 wt. %, one or more auxiliary substance(s) 0 to 15wt. %,wherein the proportions by weight add up to 100 wt. % and theproportions by weight are based on the total weight of the curablecomposition.

The term “auxiliary substances” covers components that are present inminor quantities, for example curing catalysts, adhesion promoters,water scavengers, UV stabilizers, anti-ageing agents, rheologicalauxiliaries, pigments or pigment pastes, fungicides, flame retardantsand/or solvents.

With regard to the preferred representatives of the individualcomponents and the preferably used quantities thereof, the statementsmade above in the description of the respective components apply.

The production of the composition according to the invention takes placeby known methods by intimate mixing of the components in suitabledispersing apparatus, for example a high-speed mixer.

The present invention also provides adhesive, sealant, or coatingmaterials comprising the curable composition according to invention anduse of the curable composition according to the invention as anadhesive, sealant and/or coating material.

In principle, in the present invention, all features mentioned in thecontext of the present text, in particular the embodiments, ranges ofproportions, components and other features of the composition accordingto the invention and of the uses according to the invention shown aspreferred and/or special can be implemented in all possible and notmutually exclusive combinations, with combinations of features shown aspreferred and/or special also being regarded as preferred and/orspecial.

EXAMPLES Synthesis of Phenyldimethoxysilane-Endcapped PDMS (Component X)

Phenyltrimethoxysilane (135.27 g) was placed in a 3 neck round bottomflask (0.5 L), equipped with a magnetic stirring bar a thermometer and adropping funnel. The reaction flask was flushed with nitrogen and butyllithium (0.20 g of a 2.5 M solution in hexane) was added dropwise to thesilane. The short chained PDMS polymer DMS-S12 (Mw: 300-700 g/mol; 62.53g) was charged in a dropping funnel and added slowly to the mixture overa period of 1 h, whereby the temperature of the mixture was not allowedto exceed 40° C. After complete addition, the mixture was heated to 40°C. and was left stirring at that temperature for 2 h. A sample of themixture was then taken and reacted with Titanium(IV)isopropoxide (0.10 gin a 5 g mixture) to verify the reaction completion. If gelation doesn'tset in within the first 2 min, the reaction is complete and all silanolgroups are successfully endcapped. The reaction mixture is then quenchedwith Amberlyst 15 hydrogen form (2.00 g) and left stirring for 15 h.Purification of the reaction mixture occurred via vacuum distillation.At 140° C. the excess phenyltrimethoxysilane was removed and theremaining liquid was filtered. 147.70 g of the desired polymer wereisolated.

Procedure for Manufacturing Polymer a (Polyether-BasedGamma-Silane-Terminated Polymer)

282 g (15 mmol) polypropylene glycol 18000 (hydroxyl value=6.0) wasdried in a 500 ml three-neck flask at 80-90° C. under vacuum. Under anitrogen atmosphere at 80° C., 0.1 g of dibutyltin laurate was added,and 7.2 g (32 mmol) 3-isocyanatopropyltrimethoxysilane (% NCO=18.4) wasthen added to it. After stirring for one hour at 80° C., the resultingpolymer was cooled. After adding 3 g light stabilizer (Tinuvin 770 DF)and 6 g Geniosil XL 10 to the reactor while stirring and homogenizingfor 10-30 minutes at 80° C., the resulting polymer was stored in amoisture-proof glass vessel under a nitrogen atmosphere before beingprocessed further into a curable composition.

Examples 1 and 2

Polymer A obtained according to the above procedure,phenyldimethoxysilane-endcapped PDMS (Component X) obtained according tothe above procedure, and N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane(Geniosil GF 91, Wacker) were mixed together in the speedmixer for 30 sat a speed of 2750 U/min (different ratios see table 1). The catalystdioctyltinlaurate was then added and the mixture was stirred again inthe speedmixer for additional 30 s at a speed of 2750 U/min. Theformulations described in Table 1 below were then left to cure at normalconditions for 7 days and tested for mechanical properties.

Comparative Example 1

The same procedure as Examples 1 and 2 was carried out except thatGeniosil XT55 (Wacker) was used instead of the Polymer A and thephenyldimethoxysilane-endcapped PDMS (Component X). Details aresummarized in Table 1.

Comparative Examples 2 to 5

The same procedure as Examples 1 and 2 was carried out except thatSilres IC 232 (Wacker) for Comparative Examples 2 and 3 or Silres IC 368(Wacker) for Comparative Examples 4 and 5 (Wacker) was used instead ofthe above-mentioned phenyldimethoxysilane-endcapped PDMS (Component X).Details are summarized in Table 1.

TABLE 1 Formulations and test results of Examples 1 and 2 andComparative Examples 1 to 5 Ex. 1 Ex. 2 Comp. 1 Comp. 2 Comp. 3 Comp. 4Comp. 5 Polymer A (wt. %) 49.3% 69.02% — 49.3% 69.02% 49.3% 69.02%Geniosil XT55¹⁾ — — 98.6% — — — — (wt. %) Phenyldimethoxysilane- 49.3%29.58% — — — — — endcapped PDMS (Component X) (wt. %) Silres IC 23249.3% 29.58% — — (wt. %) Silres IC 368 49.3% 29.58% (wt. %)Dioctyltinlaureate  0.4%  0.4%  0.4%  0.4%  0.4%  0.4%  0.4% (wt. %)Geniosil GF91   1%    1%   1%    1%    1%   1%   1% (wt %) SOT 85 min 46min  >5 h  3.5 h 84 min 129 min 71 min TFT <24 h   <24 h   >24 h <24 h<24 h   <24 h   <24 h   Tensile Strength 8.62 2.93 3.03 2.33 0.69 6.062.52 [N/mm²] Elongation at 119.37 212.43 218.77 139.63 101.60 234.66161.70 break (%) Optical Properties colorless, colorless, slightlycolorless, colorless, slightly slightly clear clear yellow, clear clearyellow, yellow, cloudy cloudy cloudy ¹⁾mixture of silane-terminatedpolyether and resin (Wacker)Test Method for Determining Tensile Strength and Elongation at Break

Tensile strength and elongation at break were determined according toDIN 53504. Dumbbell specimens with the following dimensions were used:thickness 2+/−0.2 mm; bar width 10+/−0.5 mm; bar length approx. 45 mm;and total length 9 cm.

Procedure: the prepolymer mixture (formulation) was spread on an evensurface forming a film with a thickness of 2 mm. The film was allowed tocure under normal conditions (23+/−2° C., relative humidity 50+/−5%) for7 days, and then the dumbbell specimen was punched out. Three specimenswere used for each determination. The test was carried out under normalconditions (23+/−2° C., relative humidity 50+/−5%) and the measurementwas carried out after 7 days of curing. The test specimens have to be atthe same temperature at which the measurement will take place. Beforethe measurement, the thickness of the test specimens is determined atleast at three different positions, at the middle and at the extremes,with a caliper. The mean value is introduced in the measuring software.The test specimens are clamped into the tensile tester so that thelongitudinal axis coincides with the mechanical axis of the tensiletester and comprises the largest possible surface of the rod heads,without clamping the middle bar. Then the dumbbell is stretched to <0.1MPa with a rate of 50 mm/min.

Then, the force-elongation curve is recorded with a line speed of 50mm/min.

Evaluation: The following values are determined—breaking force in[N/mm²] and elongation at break in [%].

Test Method for Determining SOT and TFT

The aforementioned mixtures were homogenized and applied in a frame(50×130×2 mm). Each mixture was evenly distributed so that the frame canbe completely filled. A thin polymer film was thereby obtained.

The time to form a skin (skin-over time/SOT) was determined for thesecompositions using a tool which has a rounded spatula at the tip (150×5mm). The tip of the spatula was gently contacted with the surface of thepolymer film every 1 to 5 minutes and removed carefully. The SOT wasmeasured once no more residue of the formulation remains on the spatulawhen removing it from the surface of the polymer film. Then, theresulting string must be removed from the spatula without residue. Thepolymer film returned to its original shape. In examining the SOT adifferent part of the surface of the polymer film must be used everytime. The test was performed at 23° C. and 50% relative humidity.

The time to form a tack-free surface (Tack-free time/TFT) was determinedfor these compositions using a hand test (glove protected finger). TheTFT was measured after 24 h by touching the film with a glove protectedfinger and removed it carefully from the surface of the polymer film. Ifthe resulting tack during the peal-off from the glove to the polymerfilm was achieved without any force, the polymer film was considered tobe tack-free.

The invention claimed is:
 1. A curable composition comprising a) atleast one polymer having at least one terminal group of the generalformula (I)-An-R-SiXYZ   (I), wherein A is a divalent or trivalent bonding groupcontaining at least one heteroatom, R is selected from divalenthydrocarbon residues having 1 to 12 carbon atoms, X, Y, Z are,independently of one another, selected from the group consisting of ahydroxyl group and C₁ to C₈ alkyl, C₁ to C₈ alkoxy, C₁ to C₈ acyloxygroups and-CH₂-Q-R′ wherein Q is oxygen or sulfur, and R′ is selectedfrom C₁ to C₈ alkyl groups, wherein X, Y, Z are substituents directlybound with the Si atom or the two of the substituents X, Y, Z form aring together with the Si atom to which they are bound, and at least oneof the substituents X, Y, Z is selected from the group consisting of ahydroxyl group, C₁ to C₈ alkoxy and C₁ to C₈ acyloxy groups, and n is 0or 1; and b) at least one compound of the general formula (II)

wherein R¹ is same or different and is, independently from one another,selected from the group consisting of a hydrogen atom and hydrocarbonresidues having 1 to 12 carbon atoms, R² is same or different and is,independently from one another, selected from hydrocarbon residueshaving 1 to 12 carbon atoms, Ar is selected from aryl groups, and m isan integer selected from 3 to
 9. 2. The curable composition according toclaim 1, wherein the at least one polymer has at least two terminalgroups of the general formula (I).
 3. The curable composition accordingto claim 1, wherein Ar in the general formula (II) is a phenyl group. 4.The curable composition according to claim 1, wherein R¹ and/or R² inthe general formula (II) are each independently selected from a methylor ethyl group.
 5. The curable composition according to claim 1, whereinm in the general formula (II) is an integer from 3 to
 6. 6. The curablecomposition according to claim 1, wherein the composition comprises theat least one compound of the general formula (II) in an amount of 1 to60 wt. % based on the total weight of the composition.
 7. The curablecomposition according to claim 1, wherein the divalent or trivalentbonding group A in the general formula (I) is an oxygen atom, an group,wherein R″ is selected from the group consisting of a hydrogen atom andalkyl or aryl residues having 1 to 12 carbon atoms, or is a substitutedor unsubstituted amide, carbamate, urethane, urea, imino, carboxylate,carbamoyl, amidino, carbonate, sulfonate, or sulfinate group.
 8. Thecurable composition according to claim 1, wherein the substituents X, Y,Z in the general formula (I) are, independently of one another, selectedfrom a hydroxyl, a methyl, an ethyl, a methoxy, or an ethoxy group,wherein at least one of the substituents is a hydroxyl group, or amethoxy or an ethoxy group.
 9. The curable composition according toclaim 1, wherein R in the general formula (I) is selected from amethylene, ethylene, or n-propylene group.
 10. The curable compositionaccording to claim 1, consisting of the at least one polymer having atleast one terminal group of the general formula (I) and the at least onecompound of the general formula (II).
 11. The curable compositionaccording to claim 1, further comprising at least one filler.
 12. Thecurable composition according to claim 1, wherein further comprising atleast one adhesion promoter and/or at least one catalyst.
 13. Anadhesive, sealant, or coating material comprising the curablecomposition according to claim
 1. 14. Cured reaction products of thecurable composition according to claim 1.